This invention relates to a display device, and more particularly to a display device for driving a display panel which comprises a segmental electrode and a common electrode and which is controlled according to both polarities of an applied voltage.
Conventionally, there are various kinds of electric display devices such as Nixie tubes, liquid crystals, and arrays of LED (light emitting diodes). These display devices are controlled according to only one polarity of an applied voltage.
Recently, there has been introduced a new electrophoretic display device, as disclosed for example by U.S. Pat. No. 3,668,106. The electrophoretic display panel has segmental electrodes and a common electrode, and it is driven by both polarities of the applied voltage. That is, in order to control the operation of the electrophoretic display panel, it is necessary to apply voltage of both polarities. For example, the segmental electrode shows a white color when a positive voltage is applied between the segmental electrode and the common electrode, and shows a black color when a negative voltage is applied therebetween. Even when the applied voltage is withdrawn, the color shown by the electrophoretic display panel at the time the voltage is applied remains. Such a memory characteristic is not possessed by such a conventional display panel as one made up of Nixie tubes, liquid crystals or arrays of LED.
In order for such a novel display panel to be practically useful, it is necessary to provide a novel display device for driving the panel, a device which is simple and effective, which has a small power loss and which is suitable for a display panel driven according to the both polarities of the applied voltage.